American football, parkinsonism link ‘inconclusive,’ study finds

Head injuries may increase the risk of developing the disease, data suggest

Marisa Wexler, MS avatar

by Marisa Wexler, MS |

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American football players at the professional level may be more likely to have symptoms similar to those seen in Parkinson’s disease, but the association remains inconclusive, a new study reports.

The study, “Examination of parkinsonism in former elite American football players,” was published in Parkinsonism and Related Disorders. The work was funded by the National Institute of Neurological Disorders and Stroke.

Although the causes of Parkinson’s disease are not understood, data suggest head injuries may increase the risk of developing the disease. There’s been increased attention in recent years on the risk of serious health complications from repeated head injuries from playing the sport, especially at the professional level.

Another study published this year suggested football players may be at increased risk of Parkinson’s.

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Exploring parkinsonism in football players

Researchers here enrolled 120 men who’d played professionally in the National Football League (NFL) and 58 who’d played college football. Sixty men were included as controls who had no history of playing a sport where head injuries are a concern and showed no signs of neurological disease. The men’s ages ranged from 45-74.

All the participants underwent assessments including the Unified Parkinson’s Disease Rating Scale (MDS-UPDRS) and the timed up-and-go test (TUG). The MDS-UPDRS is a standardized assessment of Parkinson’s symptoms. Its scores were used to determine if participants had Parkinson’s-like motor symptoms, referred to as parkinsonism — which for this study was specifically defined as bradykinesia (slowed movements) plus tremor  and/or rigidity. TUG is a motor function assessment that measures how long it takes to stand up from a chair, walk a short distance, turn around, return, and sit down.

“This study characterized parkinsonism, motor performance, and gait speed and mobility in a large sample of former American football players compared with similar age asymptomatic unexposed men,” the researchers wrote. “While the sample sizes were small, this is one of the largest prospective studies of parkinsonism in former elite American football players.”

Results showed that 13.3% of the former NFL players met criteria for parkinsonism, including one who’d been diagnosed with Parkinson’s disease. Parkinsonism also was found in 10.3% of former college football players and in 3.3% of the control group.

The risk of parkinsonism was significantly elevated for former professional players, statistical analyses showed, but the difference wasn’t statistically significant for college players.

Although the rate of parkinsonism was higher in former NFL players than controls, the overall rate of it in former players was fairly low, even among men who’d played professionally, the researchers noted. Nearly nine in 10 showed no signs of parkinsonism.

Snce the control group was selected to include people without signs of neurological disease, the study design likely exaggerated the difference in parkinsonism risk for people who played football compared to the general population, the researchers said.

“[T]he association between American football play and parkinsonism is inconclusive and likely dependent on factors related to sample selection and size and comparison groups used among other methodological reasons,” they said.

Former NFL players performed significantly worse on average on TUG than controls. There was no significant difference between controls and college players. Those who showed signs of chronic traumatic encephalopathy (CTE), a type of brain injury common in football players, tended to perform worse on TUG.

“The causes of these findings are unclear and likely multifaceted,” wrote the researchers who noted that, apart from neurological problems, football players often have muscle or joint issues that may hamper clear interpretations of the data.